This invention relates to a shear device for well service tools; and more particularly relates to a novel and improved shear device for disposition in a sandline and rod fishing tool whereby to prevent excess strain and loss of sandline.
In producing wells, it is often desirable to service the well with a sandline having a fishing tool which can be run down the production string to retrieve other tools. However, should the fishing tool become stuck and too much lifting force is applied, it can rupture the sandline thereby resulting in loss of extended lengths of the line and time-consuming and costly repair and replacement.
In the past, shearing devices have been employed in downhole operations, such as, for example, a pulling tool for retrieving well tools from a well bore as disclosed in U.S. Pat. No. 4,558,895 to J. W. Tamplen. In Tamplen, however, the shear pins are positioned within the tool itself and could not be effectively employed in a producing well. A similar approach is taken in U.S. Pat. No. 5,066,060 to A. G. Cooksey et al in which emergency shear screws and lockout lugs are employed in combination to permit withdrawal of a running tool in the event that an excessive force is applied. U.S. Pat. No. 4,445,572 to D. H. Fineberg et al discloses the use of a shear ring employed as a part of an unrestricted bore safety joint; and in U.S. Pat. No. 3,327,784 to G. H. Pardue an arrangement is provided for applying a hammering action to cause a plunger to shear a shear pin in the event that a fish is frozen in a well bore. U.S. Pat. No. 4,411,546 to Fischer discloses a shear tool for oil well sucker rods in which an elongated rod with a shear section is sealed within a sleeve to prevent deflection of the shear section but does not afford adequate sealing between the sleeve and shear section; and since the sleeve is not positively attached to the upper portion of the shear rod there is no assurance that the sleeve will be removed with the severed upper portion of the shear rod in the event of rupture when being extracted out of the hole, particularly if the sleeve is forced to pass through oil, scale, water and other foreign materials in the well as it is being extracted. Other representative patents in this field are U.S. Pat. Nos. 2,296,397 to A. Muhlbach, 2,605,131 to S. Marshall et al, 2,908,525 to E. N. Jones, 4,127,297 to A. Dufrene, 4,275,786 to A. G. Lee and 4,332,410 to J. R. Baker but which are largely concerned with cased hole and electrical wireline tools but not with well service tools for pumping wells.
There is a need for a shear device which can be directly incorporated into a sandline and which will, in response to a predetermined tensile force or load, rupture at the end of the line above the fishing tool in order to prevent loss of the sandline. An outer protective sleeve is so connected to the upper portion of the shear tool and sandline as to assure retrieval of the sleeve with the upper portion of the tube in a single fishing operation; and a novel and improved seal assembly at opposite ends of the sleeve will prevent seepage between the sleeve and shear rod which would otherwise destroy the integrity of the tool.